'''Multicast Source Discovery Protocol''' is a [[protocol]] that allowsdesigned to interconnectallow two different [[Sparse_multicast|PIM-SM]] [[multicast]] [[domains]] to interconnect. This allowsenables PIM-SM to have RP [[redundancy|RP redundancy]] and inter-___domaininterdomain multicasting. It is described in more detail in experimental [[Request_for_Comments|RFC]] multicasts3618.